The present invention is with respect to an apparatus for bonding or gluing running lengths of wood rod or section for making wood girders, as for example T and I girders, using high frequency heating, and made up of a support on which the lengths of wood may be rested in lined-up condition, a pressing system for pressing the said lengths from the side with a force acting towards at least one bond between the said lengths, and a transporter for moving the pressed-together girder, made up of the said lengths, between and past fixed electrodes of a HF heating system.
HF gluing or bonding for structures made of wood has, it is true, been used for a number of decades, but however in the trade it is limited to a small number of purposes, because the forms of the bonded join generally do not keep to the right conditions for such HF bonding or because it is not possible to keep to the tight size limits on producing the separate parts of the wood structure and piecing them together. For this reason wood girders for trusses, ties, supports etc. are so far produced using normal ways of bonding. In the case of T and I girders for this reason the flanges are grooved to take up the edges of the web and then, after coating with glue are placed on the web. For making such girders or sections one process using HF bonding has been put forward in the case of which the girder is placed flat on a support, that is to say with the web parallel to the support and endless pressing belts are used for taking up the girder and acting on the sides thereof. These pressing belts, having at the same time a transport function as well as a pressing function, are responsible for moving the girder past the fixed-position electrodes of the HF unit so that the glue or other bonding material goes into a solid condition, the completed girder then being freed after coming from the HF unit.
It will be seen that this process is in a certain sense continuous, this lowering the price of making the girder, but however so far the desired quality has not been produced, inasmuch as the girders coming off the plant are not truly straight with respect to the flanges or the web along the length of the girder; and furthermore the bonded join is of low quality because it would seem that the pressing belts are not able to keep the join with the adhesive in it fully pressed together.